1. Field of the Invention
The present invention relates to an endoscope that includes a first barrel and a second barrel in an image pickup optical system.
2. Description of the Related Art
Conventionally, endoscopes are used in, e.g., an industrial field and a medical field. With an endoscope, observation is performed by inserting an elongated insertion portion into, e.g., a structure or a living body. In general, in a distal end portion included in an insertion portion, an illumination optical system and an image pickup optical system included in an observation optical section are incorporated. The illumination optical system illuminates an inside of the structure or an inside of the living body. The image pickup optical system shoots an image of the inside of the structure or the inside of the living body illuminated by the illumination optical system.
The image pickup optical system includes, for example, an objective optical section and an image pickup optical section, and after focusing adjustment, the objective optical section and the image pickup optical section are integrally fixed. More specifically, the objective optical section includes a plurality of optical lenses and a first barrel, which is a lens barrel.
In the first barrel, the plurality of optical lenses is housed and fixed. The image pickup optical section includes a solid image pickup device, such as a CCD or a C-MOS sensor, and a second barrel, which is a device barrel. In the second barrel, the solid image pickup device is housed and fixed. Then, the lens barrel in the objective optical section and the device barrel in the image pickup optical section are fitted together. Then, focusing is performed by adjusting positions in an axial direction of the lens barrel and the device barrel. After completion of the focusing, the lens barrel and the device barrel are integrally fixed to form the image pickup optical system.
For example, Japanese Patent Application Laid-Open Publication No. 2006-267166 discloses an objective section of an endoscope. In the objective section of the endoscope, two objective barrels that incorporate objective members for forming an optical image of an object (corresponding to barrels in the present invention) can be bonded and adhered to each other in an air-tight manner without a decrease in optical performance. In Japanese Patent Application Laid-Open Publication No. 2006-267166, a covering that covers the entire outer circumferential faces of boundary portions of the two objective barrels with no space is provided in such a manner that the covering extends across both of the outer circumferential faces of the two objective barrels, and then, the two objective barrels and the covering are adhered to each other in an air-tight manner via brazing, soldering or welding.